1. Field of the Invention
The present invention relates to a portable terminal. More particularly, the present invention relates to a hinge apparatus for a portable terminal which interconnects a pair of housings in such a manner that the housings are capable of rotating either toward one another or away from each other.
2. Description of the Related Art
Typically, portable terminals may be classified as bar-type, flip-type, or folder type terminals.
A bar-type terminal is a type of portable terminal that includes a single body housing having input/output means and receiver/transmitter modules. The input means, typically a key pad, is always exposed in this type of terminal, which may result in malfunctions. Furthermore, in such a bar-type terminal, there is a limit to the potential size reduction of the terminal because a certain distance must be provided between the receiver module and the transmitter module.
A flip-type terminal is a type of portable terminal that includes a body, a flip and a hinge apparatus interconnecting the body and the flip so that they are opposed to each other. The data input/output means and receiver/transmitter modules are provided in the body. The flip covers the data input means, typically a key pad, to prevent malfunctions. However, similar to the bar-type terminals, there is a limit to the size reduction of flip-type terminals due to the requirement for a certain distance between the transmitter module and the receiver module.
A folder-type terminal is a type of portable terminal that includes a body, a folder, and a hinge apparatus for rotatably interconnecting the body and the folder. The folder-type terminal is opened and closed by rotating the folder. When the folder is closed with respect to the body, the folder-type terminal is set to a standby mode, and malfunctions of the data input means (i.e., the key pad) can be prevented. In addition, the transmitter module and the receiver module are provided in the body and the folder, respectively. Therefore, when the folder is opened to enter a communication mode, it is possible to secure a sufficient distance between the transmitter module and the receiver module.
A conventional hinge apparatus is disclosed in Korean Patent Registration No. 296,038 issued on May 7, 2001, which corresponds to U.S. Pat. No. 6,292,980 issued on Sep. 25, 2001, to the assignee of the present application. The disclosed hinge apparatus includes a hinge cam and a hinge shaft which are formed with peaks and valleys respectively, and a coil spring for urging the hinge cam and the hinge shaft to contact each other. These components are received within a hinge housing so that a folder or flip can be opened or closed by using the elastic force of the coil spring and the curved surfaces of the peaks and valleys.
In this type of conventional hinge device that converts an elastic force provided by an elastic member into a rotational force, the intensity of the rotational force cannot be adjusted. Therefore, this type of hinge device produces an impact at the moment the folder or the flip is either folded onto the body (i.e., completely closed) or at the moment the folder is stopped when the folder or the flip is completely opened. The weight of the folder (which is provided with a display device such as a liquid crystal display) and the rotational inertia of the folder increase the impact force. The impacts produced by opening and closing the terminal not only damages the display device and the circuit devices of the terminal, but also cumulatively increases fatigue at the hinged areas between the body and the folder or between the body and the flip as the impact is repeated. Consequently, the impact may cause a fracture of the terminal. It is necessary to perform tests requiring the terminals to be opened and closed terminals hundreds of thousands to millions of times before shipping products so as to verify the endurance against fracture, and the structural stability of the terminals when opening and closing the terminals. As a result, the cost of manufacturing the terminals increases. Furthermore, the maintenance and repair costs increase due to the fractures of the terminals or damage to the circuit devices of the terminals.